1. Field of Invention
This invention relates to auger mining of coal, especially, but not limited to, bituminous coal.
2. Prior Art
The closest prior patent art known to applicant consists of the following U.S. Pat. Nos.: 864,704, 2,976,027, 1,420,918, 3,064,958 2,734,733 3,215,214 2,766,028, 3,342,276 2,772,870 3,412,816 2,797,065.
U.S. Pat. No. 3,215,214 shows cutting elements which are individually rotatable about their own individual axes but this patent does not show the combination of rotary and orbital drives which are disclosed in the present application.
U.S. Pat. No. 2,766,028 shows an expansible auger head, but it does not show applicant's expansion method nor the combination of applicant's expansion method and his rotary and orbital bit drives.
Nor do these prior patents show applicant's hollow auger head with its internal spiral or helical coal conveyor.